The invention relates to dishwashers, and more particularly to those having a heating element for heating washwater located beneath the washing tub.
In dishwashers of the type placed on the floor and usually provided with two rotating wash arm within a washing tub it is common that the heating elements which are necessary for heating the washwater are mounted close to the bottom of the washing tub. In dishwashers which are placed on a work top or otherwise supported above the floor the space in the washing tub is more limited and usually it is only possible to arrange one single rotating wash arm therein which, by means of jets, applies dishwashing liquid on the articles to be washed. This wash arm is preferably placed adjacent the bottom of the washing tub, and in order not to disturb the movement of the wash arm, the heating element is arranged below the bottom of the washing tub, preferably in a receptacle adjacent the water outlet of the machine. The receptacle is divided into a circulation chamber and an outlet chamber separated by a fine sieve. The suction side of a circulation pump is connected to the circulation chamber. The receptacle is also covered by fine sieve over its upper portion adjacent the washing tub.
It has been discovered in dishwashers having the heating element situated at a low level that the liquid which should flow back to the receptacle by means of he fine sieve in order to be heated again is, to a great extent, guided over the fine sieve rather than through it. This means that the liquid level in the receptacle decreases to a level where the liquid does not surround the heating element thereby causing a risk of overheating.
It has been established that the phenomena described above results because when the heating element is activated a vapor pressure is built up between the liquid in the receptacle and the fine sieve thereby preventing liquid from flowing down into the receptacle through the openings in the fine sieve.